A micro-enzyme-multiplied immunoassay technique plate assay for antiepileptic drugs

Underutilization of antiepileptic drug monitoring in research situations has made comparison of data difficult to interpret. Experimental animal studies of the effects of antiepileptic drugs are similarly hindered by the lack of methods utilizing small blood samples to determine drug levels. To alleviate both problems, a standard enzyme-multiplied immunoassay technique (EMIT) assay was modified and scaled down. The resulting microEMIT utilizes only a fraction of the costly reagents (5.0 vs. 50.0 microliters) of the original assay and requires only 3-5 microliters of serum, easily obtainable from experimental animals. The method has been successfully tested with three major antiepileptic drugs, phenytoin (PHT), valproic acid (VPA) and carbamazepine (CBZ). The microEMIT assay, utilizing a 96-well plate, displays linear kinetics in the production of reduced nicotinamide adenine dinucleotide (NADH) for at least 8 minutes. The assay is linear from 2 to 100 micrograms PHT/ml, from 2 to 50 micrograms CBZ/ml and from 10 to 150 micrograms VPA/ml. The similarities suggest that a general adaptation for most EMIT drug assays will be possible.